Unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Computer tablets and other mobile devices, such as mobile phones, digital SLR cameras, video recorders, audio devices, and so on are moving to battery packs with two (or more) Li-ion cells in series (so-called “2S” or “3S” stacks or cells). Battery voltages of multi-stack battery packs typically range from 3.0V to 8.4V. Such devices typically are provided with their own power adapters for charging the high voltage battery packs.
The USB specification has become very popular and consumers have become used to being able to charge their USB devices from universal USB power sources. Consumers are used to USB, mini-USB, and micro-USB connectors being present in portable electronics and their use for battery charging from a USB power source. However, since a large majority of USB devices are defined at 5V, it may not be possible to charge high voltage (>5V) 2S or 3S battery packs using a typically USB power source.